Well I once had a problem with online payments since they recently introduced "Verified by Visa" as an saftey measure so that people can't steal your card then use it online.
I had to go onto my internet bank and activate it in order to do anything at all online with it. Even though I had money on it, even though the bank hadn't blocked it or anything this was still the messages I recieved when I tried to do a purchase anywhere.
Just throwing out suggestion blindly here, maybe it has nothing to do with it.